Assemblages of ground-dwelling arachnids and carabids in metal-polluted forests: Are there signs of recovery after emission reductions from the Middle Ural Copper Smelter?
Abstract
Information on the natural recovery of ground-dwelling invertebrate communities following reductions in industrial pollution is fragmentary. Assemblages of epigeic arachnids (spiders and harvestmen) and ground beetles in the southern taiga spruce-fir forests were analyzed in two areas – one background and the other polluted by long-term emissions from the Middle Ural Copper Smelter. Two periods were compared: relatively high emissions (2005) and almost cessed emissions starting from 2010 (2018). We tested the hypothesis that differences between the areas decreased by the second period compared to the first. We assessed total activity density, species richness, taxocene structure, and the abundance of groups identified based on ecological traits (body size, preferences for moisture level, stratum and habitat type, hunting strategy for arachnids, and mobility and feeding preferences for ground beetles). The hypothesis was not confirmed: differences between the areas persisted in total abundance, species richness, and taxocene structure. Some signs of recovery were observed in the arachnid assemblages: a shift towards “linifidization” (i.e., replacement of species from the family Lycosidae with species from the family Linyphiidae), an increase in harvestmen abundance, and the appearance of species previously recorded only in background forests. However, such signs were absent for ground beetles: taxocene features of contaminated areas remained intact, including an increased percentage of mixophytophages and the absence of species with large individuals.